1. Field of the Invention
The invention relates to a transmitter for angle-modulated signals having an input for synchronous binary signals, which is connected to a premodulation filter the output of which is connected to the signal input of a frequency modulation arrangement serving to provide in response to an input signal voltage an output signal at a frequency which linearly depends on the signal voltage.
2. DESCRIPTION OF THE PRIOR ART
A transmitter of the above-defined type is known from the Proceedings of the 29th IEEE Vehicular Technology Conference, Arlington, Ill., USA, Mar. 27-30, 1979, pages 13-19.
This prior art transmitter has the advantage that a good suppression of the out-of-band power spectrum is obtained so that smaller channel spacings or larger transmission rates or a higher transmission power, as the case may be, or a combination thereof may be employed.
In said prior art transmitter a low-pass filter having a pass characteristic which is a Gaussian curve, such a filter being commonly referred to as a Gaussian low-pass filter, is used as the premodulation filter.
A system comprised of a transmitter and a receiver is usually optimized for an optimal signal-to-noise ratio by means of a filter, which is commonly referred to as a post-modulation filter, in the receiver. In the above-mentioned publication a Gaussian filter is used as the post modulation filter, this filter being connected in front of the detector and being indicated as a predetection filter.
It is an object of the invention to provide a transmitter of the type defined in the preamble, in which the suppression of the out-of-band power spectrum is at least equally good as that of the known transmitter, which, however, can accomplish in the system of transmitter and receiver a significant improvement of the error rate as a function of the signal-to-noise ratio.